Coupling of individual quantum emitters to channel plasmons.

Efficient light-matter interaction lies at the heart of many emerging technologies that seek on-chip integration of solid-state photonic systems. Plasmonic waveguides, which guide the radiation in the form of strongly confined surface plasmon-polariton modes, represent a promising solution to manipulate single photons in coplanar architectures with unprecedented small footprints. Here we demonstrate coupling of the emission from a single quantum emitter to the channel plasmon polaritons supported by a V-groove plasmonic waveguide. Extensive theoretical simulations enable us to determine the position and orientation of the quantum emitter for optimum coupling. Concomitantly with these predictions, we demonstrate experimentally that 42% of a single nitrogen-vacancy centre emission efficiently couples into the supported modes of the V-groove. This work paves the way towards practical realization of efficient and long distance transfer of energy for integrated solid-state quantum systems.E.B.-U., R.M., M.G. and R.Q. acknowledge the European Community’s Seventh Framework Programme (grant ERC- Plasmolight; no. 259196) and Fundació privada CELLEX. E.B.-U. acknowledges support of the FPI fellowship from the Spanish MICINN. R.M. acknowledges support of Marie Curie and NEST fellowships. C.G.-B. and F.J.G.-V. acknowledge the European Research Council (ERC-2011-AdG, Proposal No. 290981). C.G.-B., E.M., and F.J.G.-V. acknowledge the Spanish MINECO (Contract No. MAT2011-28581-C02-01). C.G.-B. acknowledges support of the FPU fellowship from the Spanish MECD. I.P.R., T.H. and S.I.B. acknowledge financial support for this work from the Danish Council for Independent Research (the FTP project ANAP, Contract No. 09-072949) and from the European Research Council, Grant No. 341054 (PLAQNAP). Y.A. acknowledges the support of RYC-2011-08471 fellowship from MICINN. We thank Luis Martin-Moreno and Cesar E. García for fruitful discussions, Jana M. Say and Louise J. Brown for providing the ND solution, and Ioannis Tsioutsios for support with the AFM manipulation technique.This is the final published version. It first appeared at http://www.nature.com/ncomms/2015/150807/ncomms8883/full/ncomms8883.html

A synthetic growth switch based on controlled expression of RNA polymerase

International audienceThe ability to control growth is essential for fundamental studies of bacterial physiology and biotechnological applications. We have engineered an Escherichia coli strain in which the transcription of a key component of the gene expression machinery, RNA polymerase, is under the control of an inducible promoter. By changing the inducer concentration in the medium, we can adjust the RNA polymerase concentration and thereby switch bacterial growth between zero and the maximal growth rate supported by the medium. We show that our synthetic growth switch functions in a medium-independent and reversible way, and we provide evidence that the switching phenotype arises from the ultrasensitive response of the growth rate to the concentration of RNA polymerase. We present an application of the growth switch in which both the wild-type E. coli strain and our modified strain are endowed with the capacity to produce glycerol when growing on glucose. Cells in which growth has been switched off continue to be metabolically active and harness the energy gain to produce glycerol at a twofold higher yield than in cells with natural control of RNA polymerase expression. Remarkably, without any further optimization, the improved yield is close to the theoretical maximum computed from a flux balance model of E. coli metabolism. The proposed synthetic growth switch is a promising tool for gaining a better understanding of bacterial physiology and for applications in synthetic biology and biotechnology

Watt-class CMOS-compatible power amplifier

Power amplifier is becoming a critical component for integrated photonics as the integrated devices try to carve out a niche in the world of real-world applications of photonics. That is because the signal generated from an integrated device severely lacks in power which is due mainly to the small size which, although gives size and weight advantage, limits the energy storage capacity of an integrated device due to the small volume, causing it to rely on its bench-top counterpart for signal amplification downstream. Therefore, an integrated high-power signal booster can play a major role by replacing these large solid-state and fiber-based benchtop systems. For decades, large mode area (LMA) technology has played a disruptive role by increasing the signal power and energy by orders of magnitude in the fiber-based lasers and amplifiers. Thanks to the capability of LMA fiber to support significantly larger optical modes the energy storage and handling capability has significantly increased. Such an LMA device on an integrated platform can play an important role for high power applications. In this work, we demonstrate LMA waveguide based CMOS compatible watt-class power amplifier with an on-chip output power reaching ~ 1W within a footprint of ~4mm2.The power achieved is comparable and even surpasses many fiber-based amplifiers. We believe this work opens up opportunities for integrated photonics to find real world application on-par with its benchtop counterpart

Watt-class silicon photonics-based optical high-power amplifier

High-power amplifiers are critical components in optical systems spanning from long-range optical sensing and optical communication systems to micromachining and medical surgery. Today, integrated photonics with its promise of large reductions in size, weight and cost cannot be used in these applications, owing to the lack of on-chip high-power amplifiers. Integrated devices severely lack in output power owing to their small size, which limits their energy storage capacity. For the past two decades, large mode area (LMA) technology has played a disruptive role in fibre amplifiers, enabling a dramatic increase of output power and energy by orders of magnitude. Owing to the ability of LMA fibres to support significantly larger optical modes, the energy storage and power handling capabilities of LMA fibres have significantly increased. Therefore, an LMA device on an integrated platform can play a similar role in power and energy scaling of integrated devices. In this work, we demonstrate LMA waveguide-based watt-class high-power amplifiers in silicon photonics with an on-chip output power exceeding ~1 W within a footprint of only ~4.4 mm2. The power achieved is comparable and even surpasses that of many fibre-based amplifiers. We believe that this work has the potential to radically change the integrated photonics application landscape, allowing power levels previously unimaginable from an integrated device to replace much of today’s benchtop systems. Moreover, mass producibility, reduced size, weight and cost will enable yet unforeseen applications of laser technology

Sub-2W tunable laser based on silicon photonics power amplifier

High-power tunable lasers are intensely pursued due to their vast application potential such as in telecom, ranging, and molecular sensing. Integrated photonics, however, is usually considered not suitable for high-power applications mainly due to its small size which limits the energy storage capacity and, therefore, the output power. In the late 90s, to improve the beam quality and increase the stored energy, large-mode-area (LMA) fibers were introduced in which the optical mode area is substantially large. Such LMA fibers have transformed the high-power capability of fiber systems ever since. Introducing such an LMA technology at the chip-scale can play an equally disruptive role with high power signal generation from an integrated photonics system. To this end, in this work we demonstrate such a technology, and show a very high-power tunable laser with the help of a silicon photonics based LMA power amplifier. We show output power reaching 1.8 W over a tunability range of 60 nm, spanning from 1.83 µm to 1.89 µm, limited only by the seed laser. Such an integrated LMA device can be used to substantially increase the power of the existing integrated tunable lasers currently limited to a few tens of milliwatts. The power levels demonstrated here reach and surpass that of many benchtop systems which truly makes the silicon photonics based integrated LMA device poised towards mass deployment for high power applications without relying on benchtop systems.</p

Towards On-Chip Ultrafast Pulse Amplification

Amplification of ultrafast optical signals is key to a large number of applications in photonics. While ultashort pulse amplification is well established in optical gain fibers, it is challenging to achieve in photonic-chip integrated waveguides. Recently, several integrated (quasi-)continuous-wave amplifiers have been demonstrated, based on rare-earth, heterogeneous semiconductor integration or nonlinear parametric gain [1]–[4]. On-chip amplification of ultrafast pulses, however, remains challenging due to the inherently small mode area and high-optical nonlinearity in integrated waveguides

Femtosecond pulse amplification on a chip

Femtosecond laser pulses enable the synthesis of light across the electromagnetic spectrum and provide access to ultrafast phenomena in physics, biology, and chemistry. Chip-integration of femtosecond technology could revolutionize applications such as point-of-care diagnostics, bio-medical imaging, portable chemical sensing, or autonomous navigation. However, current chip-integrated pulse sources lack the required peak power, and on-chip amplification of femtosecond pulses has been an unresolved challenge. Here, addressing this challenge, we report &gt;50-fold amplification of 1 GHz-repetition-rate chirped femtosecond pulses in a CMOS-compatible photonic chip to 800 W peak power with 116 fs pulse duration. This power level is 2–3 orders of magnitude higher compared to those in previously demonstrated on-chip pulse sources and can provide the power needed to address key applications. To achieve this, detrimental nonlinear effects are mitigated through all-normal dispersion, large mode-area and rare-earth-doped gain waveguides. These results offer a pathway to chip-integrated femtosecond technology with peak power levels characteristic of table-top sources.</p

Silicon photonics-based high-energy passively Q-switched laser

Chip-scale, high-energy optical pulse generation is becoming increasingly important as integrated optics expands into space and medical applications where miniaturization is needed. Q-switching of the laser cavity was historically the first technique to generate high-energy pulses, and typically such systems are in the realm of large bench-top solid-state lasers and fibre lasers, especially in the long wavelength range &gt;1.8 µm, thanks to their large energy storage capacity. However, in integrated photonics, the very property of tight mode confinement that enables a small form factor becomes an impediment to high-energy applications owing to small optical mode cross-sections. Here we demonstrate a high-energy silicon photonics-based passively Q-switched laser with a compact footprint using a rare-earth gain-based large-mode-area waveguide. We demonstrate high on-chip output pulse energies of &gt;150 nJ and 250 ns pulse duration in a single transverse fundamental mode in the retina-safe spectral region (1.9 µm), with a slope efficiency of ~40% in a footprint of ~9 mm2. The high-energy pulse generation demonstrated in this work is comparable to or in many cases exceeds that of Q-switched fibre lasers. This bodes well for field applications in medicine and space.</p